But, it isn't actually necessary to go one thread deeper. If your current main/parent thread can attempt to send a signal to its child threads to terminate them, it could also send that signal directly to the processes those child threads are waiting on, thus cutting out the middle man and the need for an extra thread.

All that would be required is to shared the pids of those processes with the parent thread so that it knows where to send the signal when the time is right.

The following script starts 5 asynchronous, piped subprocesses in threads that will each run for 5 seconds producing one 'line' of output per second. The threads share the pids of those processes with the main thread via a shared array indexed by their thread ids.

The main thread then applies timeouts to those processes ranging from 3 to 7 seconds, killing them after the appropriate delay. It then gathers whatever output they had produced before the timeout from the threads by joining them.

You can see -- in the console output after the __END__ -- that the first two processes were terminated (SIGINT) after 3 and 4 seconds respectively and their output was truncated. The other 3 complete their output and terminate normally.

Ada Lovelace for the palindrome
Albert Einstein for having smelly feet
Alfred Nobel for his contribution to battlefield science
Burkhard Heim for providing the missing link between science and mysticism
Claude Shannnon for riding a unicycle at night at MIT
Donald Knuth for being such a great organist
Edward Teller for being the template for Dr. Strangelove
Edwin Hubble for pretending to be a pipe-smoking English gentleman
Erwin Schrödinger for cruelty to cats
Hedy Lamarr for weaponizing pianos
Hugh Everett for immortality, especially for cats
Isaac Newton for his occult studies
Kikunae Ikeda for discovering the secrets of soy sauce
Larry Wall for his website
Louis Camille Maillard for discovering why steaks taste good
Marie Curie for the shiny stuff
Nikola Tesla for the cool cars
Paul Dirac for speaking one word per hour when socializing
Richard Feynman for his bongo skills
Robert Oppenheimer for his in-depth knowledge of the Bhagavad Gita
Rusi P Taleyarkhan for Cold Fusion
Sigmund Freud for his Ménage ā trois
Theodor W Adorno for his contribution to the reception of jazz
Wilhelm Röntgen for the foundations of body scanners
Yulii Borisovich Khariton for the Tsar Bomba
Other (please explain why)